Remember most people here really do know how you feel. I was determined diabetes wasn't going to rule me, I was going to rule it. Having said that, I must admit I haven't always been successful.
If you don't feel comfortable talking to the diabetic nurses or doctors, try finding a Young Diabetic group - most clinics run them. I found it really good talking to people my own age (most groups were 18-25) and finding I wasn't the only one with these issues and different people have different ideas of 'fix its', it's really good to bounce ideas of each other.
As for stopping you doing what you want- Sir Steve Redgrave, Halle Berry - also diabetic. Go back in time Gary Mabbut (professional footballer) and I'm sure many more. These people show diabetes does not mean you can't do things.